Oscillating bearing

ABSTRACT

An oscillating bearing arrangement, for axial piston pumps ( 1 ) of a wobble plate type, comprises a shaft ( 6 ) connected for rotation about its longitudinal axis ( 13 ) to a wobble plate, the shaft ( 6 ) being coupled with a shaft bearing ( 3 ) arranged in a housing ( 4 ) and comprises an inner ring ( 15 ) and an outer ring ( 16 ), and oscillating driven elements ( 14 ) being spring-suspended against the wobble plate characterized in that the wobble plate ( 23 ) which is substantially trapezoidal-shaped in longitudinal section is arranged concentrically in a reception bore of the inner ring ( 15 ) of the shaft ( 3 ).

FIELD OF THE INVENTION

The invention concerns an oscillating bearing arrangement, particularlyfor axial piston pumps of a wobble plate type, comprising a shaftconnected for rotation about its longitudinal axial to a wobble plate,the shaft being coupled with a shaft bearing arranged in a housing andcomprising an inner ring and an outer ring, and oscillating drivenelements being spring-suspended against the wobble plate.

BACKGROUND OF THE INVENTION

An axial piston pump having an oscillating bearing arrangement of thepre-cited type is known from FR 27 21 352. The shaft connected to thewobble plate is mounted for rotation by two spaced-apart shaft bearingseach of which comprises an inner ring and an outer ring. When the shaftis driven, its rotary motion is converted into a reciprocating motion bythe wobble plate.

A drawback of this is that the wobble plate is arranged outside of theshaft bearing in axial direction, so that high forces of tilt arisewhich have to be taken up by a second shaft bearing. This arrangement ofthe shaft bearings and the wobble plate results in a large axial designspace requirement.

SUMMARY OF THE INVENTION

The object of the invention is to create an oscillating bearingarrangement whose axial design space requirement is as small aspossible.

The invention achieves the object wherein an oscillating bearingarrangement, for axial piston pumps (1) of a wobble plate type,comprises a shaft (6) connected for rotation about its longitudinal axis(13) to a wobble plate, the shaft (6) being coupled with a shaft bearing(3) arranged in a housing (4) and comprises an inner ring (15) and anouter ring (16), and oscillating driven elements (14) beingspring-suspended against the wobble plate by the fact that the wobbleplate which is substantially trapezoidal-shaped in longitudinal sectionis arranged concentrically in the reception bore of the inner ring ofthe shaft bearing.

The shaft is connected to the inner ring and/or to the wobble plate by acoupling element. This facilitates the assembly of the oscillatingbearing arrangement.

The inner ring is configured as a pot-shaped sheet metal part made bynon-chipping shaping and comprising a tubular section which is parallelto the longitudinal axis of the shaft and comprises a ball race grooveformed chiplessly therein. The tubular section is closed at one end by abottom which comprises a recess for the coupling element.

Due to the inventive arrangement of the wobble plate within the pitchcircle diameter of the rolling elements of the oscillating bearing, thestatic and dynamic conditions are improved because the center point ofthe bearing and the point of application of the force resultant on thewobble plate approach each other. Due to the lodging of the wobble platein the inner ring, the diameter of the shaft bearing is increased sothat higher dynamic and static basic load ratings are also achieved. Inaddition, the construction of the invention has a substantially reducedaxial design space requirement because, compared to the prior art, lowerforces of tilt occur so that one of the shaft bearings can be omitted.

Further advantageous features of the invention are described in claims 2to 8.

According to claim 2, the shaft is connected to the inner ring and/or tothe wobble plate by a coupling element. This facilitates the assembly ofthe oscillating bearing arrangement.

According to claim 3, the inner ring is configured as a pot-shaped sheetmetal part made by non-chipping shaping and comprising a tubular sectionwhich is parallel to the longitudinal axis of the shaft and comprises aball race groove formed chiplessly therein. The tubular section isclosed at one end by a bottom which comprises a recess for the couplingelement.

Such an inner ring is not only simple and economical to manufacturebecause of being made by non-chipping shaping, but it also has theadvantage that its outer surface which is in contact with a sealing lipof a seal is sufficiently smooth and thus does not need to be finishedby machining.

The same advantages are also obtained with an outer ring which islikewise configured as a sheet metal part which is made by non-chippingshaping and comprises a ball race groove formed chiplessly on its innerperipheral surface, and a sealing ring is arranged between the innerring and the outer ring. It is, of course, also possible to make thebearing rings by a chipping method.

According to a further feature of the invention, the wobble comprises,on its end face facing the bottom, a recess for the coupling element,and, on its end face facing the driven elements, a cover plate.

The wobble plate and/or the cover plate can be made of differentmaterials and by different manufacturing methods. They are made of ametal or a plastic by machining, casting, sintering or injectionmolding.

According to another feature of the invention, an anti-rotation deviceis arranged between the inner ring and the wobble plate to prevent anundesired rotation of the wobble plate in the inner ring.

Finally, according to still another feature of the invention, the axialpiston pump is used for a direct injection of fuel, and the shaft is acamshaft of an internal combustion engine. This has the advantage thatno additional drive is required for the axial piston pump and theoscillating bearing arrangement of the invention has a particularlysmall construction space required in the automobile.

The invention will now be described more closely with reference to thefollowing example of embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a longitudinal section through a prior art axial pistonpump in the region of the oscillating bearing, and

FIG. 2 shows a longitudinal section through an oscillating bearing ofthe invention, and an associated drive shaft.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a prior art axial piston pump 1 in which an oscillatingbearing 2 is mounted on two spaced-apart shaft bearings 3 in a housing4. The oscillating bearing 2 can be driven by a shaft 6 connected to anengine 5. The oscillating bearing 2 comprises a first, bellied bearingring 7 which is connected to the shaft 6 by a screw connection 8. Therolling elements 10 which are arranged in a cage 9 support a secondbearing ring 11 of the oscillating bearing 2 whose end face 12 isinclined at a defined angle to a central vertical line of thelongitudinal axis 11 of the shaft 6 and forms a contact surface for thepistons 14.

Each of the shaft bearings 3 is made up of an inner ring 15, an outerring 16 and associated bearing balls 17 which are arranged in a cage 18.The rotation of the shaft 6 caused by the engine 5 is converted into areciprocating motion of the pistons 14 by the screw connection 8, thefirst bearing ring 7 and the second bearing ring 11 of the oscillatingbearing 2.

The oscillating bearing arrangement of the invention shown in FIG. 2comprises a chiplessly drawn inner ring 15 which is configured as apot-shaped sheet metal part and comprises a tubular section 19 and abottom 20 which closes the tubular section 19 at one end. The inner ring15 is surrounded by the outer ring 16, and bearing balls 17 guided in acage 18 roll between the two rings. A seal 22 arranged between the innerring 15 and the outer ring 16 seals the bearing in the direction towardthe engine.

According to the invention, a wobble plate 2 having a substantiallytrapezoidal shape in longitudinal section is arranged in the receptionbore of the inner ring 15 and covered with a cover plate 24 whichcooperates with the pistons 14 in a manner not shown. An anti-rotationdevice 25 is arranged between the wobble plate 23 and the inner ring 15to prevent a rotation of the wobble plate 23 in the inner ring 15. Thestatic sealing is achieved by two O-ring seals 26 and 29. Both thebottom 20 of the inner ring 15 and the wobble plate 25 comprise a recess27 into which a coupling element 28 engages. At its other end, thiscoupling element 28 is connected to the shaft 6 through a further recess21. The coupling element 28 can be configured, for instance, as alow-cost Oldham coupling and assures that the rotation of the shaft 6caused by an engine 5 likewise causes a rotation of the inner ring 15 ofthe bearing which, finally, through the cover plate 24 of the wobbleplate 23, leads to a reciprocating motion of the pistons 14.

If one replaces the shaft bearing 3 described in fig. 1 with theoscillating bearing of the invention, it becomes clear at a glance thata considerable shortening of the axial design space is achieved becauseone of the shaft bearings 3 can be dispensed with completely.

What is claimed is:
 1. An oscillating bearing arrangement, for axialpiston pumps (1) of a wobble plate type, comprising a shaft (6)connected for rotation about its longitudinal axis (13) to a wobbleplate, the shaft (6) being coupled with a shaft bearing (3) arranged ina housing (4) and comprising an inner ring (15) and an outer ring (16),and oscillating driven elements (14) being spring-suspended against thewobble plate characterized in that the wobble plate (23) which issubstantially trapezoidal-shaped in longitudinal section is arrangedconcentrically in a reception bore of the inner ring (15) of the shaft(3).
 2. An oscillating bearing arrangement according to claim 1,characterized in that the shaft (6) is connected to the inner ring (15)and/or to the wobble plate (23) by a coupling element (28).
 3. Anoscillating bearing arrangement according to claim 1, characterized inthat the inner ring (15) is configured as a pot-shaped sheet metal partmade by non-chipping shaping and comprises a tubular section (19) whichis parallel to the longitudinal axis (13) of the shaft (6) and comprisesa ball race groove formed chiplessly therein, the tubular section (19)being closed at one end by a bottom (20) which comprises a recess (27)for the coupling element (28).
 4. An oscillating bearing arrangementaccording to claim 1, characterized in that the outer ring (16) isconfigured as a sheet metal part which is made by non-chipping shapingand comprises a ball race groove formed chiplessly on its innerperipheral surface, and a sealing ring (22) is arranged between theinner ring (15) and the outer ring (16).
 5. An oscillating bearingarrangement according to claim 1, characterized in that the wobble plate(23) comprises, on its end face facing bottom (20), a recess (27) for acoupling element (28), and, on its end face facing the driven elements(14), a cover plate (24).
 6. An oscillating bearing arrangementaccording to claim 1, characterized in that the wobble plate (23) and/ora cover plate (24) are made of a metal or a plastic by machining,casting, sintering or injection molding.
 7. An oscillating bearingarrangement according to claim 1, characterized in that an anti-rotationdevice (25) is arranged between the inner ring (15) and the wobble plate(23).
 8. An oscillating bearing arrangement according to claims 1characterized in that the axial piston pump (1) is used for directinjection of fuel, and the shaft (6) is a camshaft or an internalcombustion engine.